The Development of Behavior Before Birth

Study of the fetus in vivo provides a simple system for experimental study of early neurobehavioral development. This review summarizes research on the development of behavior before birth including studies where fetuses are exposed to stimuli that mimic features of the neonatal environment, such as milk and an artificial nipple. These stimuli reliably evoke responses from fetal subjects, including species-typical behavior such as the stretch response and oral grasping of the artificial nipple. Contingent presentations of the nipple and milk can result in classical conditioning, including activation of the endogenous opioid system. Quantitative analysis of fetal motor behavior coupled with the use of ecologically relevant sensory manipulations provide a means for assessing integrated output of the developing nervous system.